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RFC 1421

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Network Working Group
Request for Comments: 1421
Obsoletes: 1113

J. Linn
IAB IRTF PSRG, IETF PEM WG
February 1993

### Privacy Enhancement for Internet Electronic Mail:
Part I: Message Encryption and Authentication Procedures

#### Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.

#### Acknowledgements

This document is the outgrowth of a series of meetings of the Privacy and Security Research Group (PSRG) of the IRTF and the PEM Working Group of the IETF. I would like to thank the members of the PSRG and the IETF PEM WG, as well as all participants in discussions on the "pem-dev@tis.com" mailing list, for their contributions to this document.

#### Table of Contents

1. Executive Summary
2. Terminology
3. Services, Constraints, and Implications
4. Processing of Messages

4.1 Message Processing Overview

4.1.1 Types of Keys
4.1.2 Processing Procedures

4.1.2.1 Processing Steps
4.1.2.2 Error Cases

4.2 Encryption Algorithms, Modes, and Parameters
4.3 Privacy Enhancement Message Transformations

4.3.1 Constraints
4.3.2 Approach

4.3.2.1 Step 1: Local Form
4.3.2.2 Step 2: Canonical Form
4.3.2.3 Step 3: Authentication and Encryption
4.3.2.4 Step 4: Printable Encoding
4.3.2.5 Summary of Transformations

4.4 Encapsulation Mechanism
4.5 Mail for Mailing Lists
4.6 Summary of Encapsulated Header Fields

4.6.1 Per-Message Encapsulated Header Fields

4.6.1.1 Proc-Type Field

4.6.1.1.1 ENCRYPTED
4.6.1.1.2 MIC-ONLY
4.6.1.1.3 MIC-CLEAR
4.6.1.1.4 CRL

4.6.1.2 Content-Domain Field
4.6.1.3 DEK-Info Field

4.6.2 Encapsulated Header Fields Normally Per-Message

4.6.2.1 Originator-ID Fields

4.6.2.1.1 Originator-ID-Asymmetric Field
4.6.2.1.2 Originator-ID-Symmetric Field

4.6.2.2 Originator-Certificate Field
4.6.2.3 MIC-Info Field

4.6.3 Encapsulated Header Fields with Variable Occurrences

4.6.3.1 Issuer-Certificate Field

4.6.4 Per-Recipient Encapsulated Header Fields

4.6.4.1 Recipient-ID Fields

4.6.4.1.1 Recipient-ID-Asymmetric Field
4.6.4.1.2 Recipient-ID-Symmetric Field

4.6.4.2 Key-Info Field

4.6.4.2.1 Symmetric Key Management
4.6.4.2.2 Asymmetric Key Management

5. Key Management

5.1 Data Encrypting Keys (DEKs)
5.2 Interchange Keys (IKs)

5.2.1 Subfield Definitions

5.2.1.1 Entity Identifier Subfield
5.2.1.2 Issuing Authority Subfield
5.2.1.3 Version/Expiration Subfield

5.2.2 IK Cryptoperiod Issues

6. User Naming
7. Example User Interface and Implementation
8. Minimum Essential Requirements
9. Descriptive Grammar
NOTES
Patent Statement
Security Considerations
Author's Address

Original text document

Next: 1. Executive Summary

Connected: An Internet Encyclopedia
RFC 1421